Azure ServiceBus relay slow in response

Hi,

Recently i came across slowness in azure service bus relay response (taking around 20-30sec)

I used Azure WCF Relay, i observed first call to the relay after some idle time is taking more time than the subsequent calls , i checked the on premise log for the one of the request and there was no delay in processing the request but in app insights shows relay took 20-30sec.

Any help to find the root cause is appreciated.

Thank you